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Evaluation of the sounding rod method for sampling coarse riverbed sediments in non-wadeable streams and rivers
Citation:
Collins, S. AND J. Flotemersch. Evaluation of the sounding rod method for sampling coarse riverbed sediments in non-wadeable streams and rivers. River Research and Applications. John Wiley & Sons Incorporated, New York, NY, 30(8):1065-1069, (2014).
Impact/Purpose:
The purpose of this document is to provide statistical support to a commonly used substrate and physical habitat mapping technique. This technique was introduced in 1997 by Kauffman and Robison as modification of, and method to overcome some of the difficulties associated with, the Wolman pebble count for use in large (non-wadeable) rivers.
Description:
The substrate of fluvial systems is regularly characterized as part of a larger physical habitat assessment. Beyond contributing to a basic scientific understanding of fluvial systems, these measures are instrumental in meeting the regulatory responsibilities of bioassessment and monitoring programs, as well as being essential to monitoring the success of restoration and rehabilitation efforts. We describe and validate a commonly-used technique for broadly categorizing, and thus characterizing, the substrate in non-wadeable streams and rivers called the sounding rod method. In brief, a rod, often hollow, is used to probe the substrate of non-wadeable systems to characterize the substrate. We tested the viability of this method on three different systems by comparing estimated particle class and direct particle measurements. Data were compared using a Wilcoxon signed-rank test, Kendall’s tau-b and a contingency table. We also used a Kruskal-Wallis test to determine if groups were significantly different. Our results indicate that substrates can adequately be defined into six broad classes (fine-particle sediment, sand, gravel, cobble, boulder, and bedrock) based on size using the sounding rod. Estimated classes were significantly positively correlated to measured classes (τ = 0.83, p < 0.001), and estimates of size class and direct measurements of size were not from significantly different distributions (χ2 0.05,9 = 569.51, p < 0.001). Further, there were significant differences between each category (H = 243.5, 3 d.f., p < 0.001). While our results affirm that actual substrate class size can be directly inferred from estimated data, it should be noted that soft sediments < 20 cm were not always detected. This finding should be carefully considered with individual study objective. Overall, the sounding rod method can be learned quickly, and it is a low-cost and time-efficient method for substrate classification.
